Multicomponent Reactions (MCRs) are one-pot reactions, in which three or more starting materials react to form a product, where basically all or most of the atoms contribute to the newly formed product. Speed, diversity, efficiency, atom-economy and environmental friendliness are some of the notable features of this class of reactions. The most important MCRs are the isocyanide-based reactions such as the Passerini three-component reaction and the Ugi four-component reaction. Moreover, a variety of heterocycles can be constructed using the MCR strategy, where zwitterionic intermediates are generated by the addition of nucleophile to activated C—C multiple bonds followed by their interception with a third component.
Arynes are highly electrophilic reactive intermediates, which have been extensively utilized in various carbon-carbon and carbon-heteroatom bond-forming reactions. One of the important aspects of aryne chemistry is multicomponent reaction, which mainly include the initial addition of nucleophiles to arynes and subsequent trapping of the aryl anion intermediate with electrophiles. If the nucleophile and electrophile do not belong to the same molecule, the overall process is a unique three-component coupling, where the aryne is inserted between the other two coupling partners (eqn (1)). This versatile transition-metal-free methodology has been applied to the synthesis of valuable heterocycles and in natural product synthesis.

Organophosphorus compounds are highly effective insecticides and widely used in synthetic organic chemistry. Some of the common applications include the use of phosphonium ylides in the Wittig reaction, the use of phosphines in the Staudinger and Mitsunobu reactions, and the use of phosphines as ligands in transition metal-mediated processes. Phosphorus and nitrogen are in group 5 in periodic table, and thus both the compounds have many similar properties. Generally organophosphorus compounds are based on the two oxidation sate of phosphorus e.g., phosphorus (V) vs phosphorus (III). Commonly organophosphorous compounds contain C—P bond (excluding phosphate and phosphate esters, which lack this kind of bonding).
In the last decade there are significant developments in aryne based MCR process. Some of the benzoxaphospholes are known to possess anti-oxidant activity. Several phosphorus-containing compounds are known to be potential insecticides, bactericides, fungicides, and antibiotic reagents, because of their biological activities, and such compounds exist widely in nature. In addition, oxaphosphole-based monophosphorus compounds are known to be excellent ligands for palladium-catalyzed amination reactions.
U.S. Pat. No. 4,250,320 discloses a process for the production of substituted benzoxaphospholes which are useful as herbicides. The substituted benzoxaphospholes are:

wherein R is selected from the group consisting of lower alkyl, lower alkoxy, C3-C8 cycloalkyl, phenyl, biphenyl, phenoxyphenyl and substituted phenyl containing from one to three substituents individually selected from the class consisting of lower alkyl, lower alkoxy, lower dialkylamino, diphenylamino, C3-C8 cycloalkyl, fluoro, chloro, trifluoromethyl and trimethylsilyl; R1 and R2 are independently selected from the group consisting of hydrogen, lower alkyl, C3-C8 cycloalkyl, and phenyl; Z is selected from the group consisting of lower alkyl, lower alkoxy, phenyl, phenoxy, lower dialkylamino, diphenylamino, C3-C8 cycloalkyl, fluoro, chloro, trifluoromethyl and trimethylsilyl; n is an integer from 0 to 2.
US4219510 discloses novel substituted benzoxaphospholes which are useful as herbicides. The novel substituted benzoxaphospholes are:
wherein;
R is selected from the group consisting of hydroxy, lower alkyl, lower alkoxy, phenyl and haloalkyl phenyl; and R1 is selected from the group consisting of hydrogen and lower alkyl.
Article titled “Three-component coupling of arynes, aminosilanes, and aldehydes” by Hiroto Yoshida et al. published in Organic Letters, 2007, 9 (17), pp 3367-3370 reports a three-component coupling of arynes, aminosilanes and aldehydes enables diverse amino and hydroxymethyl groups to be incorporated directly into 1,2-positions of aromatic rings. The reaction carried out in presence of KF and 18-Crown-6 in THF solvent.
Article titled “Efficient synthesis of quaternary and p-stereogenic phosphonium triflates” by E Remond et al published in Org. Lett., 2010, 12 (7), pp 1568-1571 reports an efficient and general method for the preparation of achiral and chiral phosphonium salts. This synthesis is based on the quaternization of phosphines and their compounds with arynes generated in situ from 2-(trimethylsilyl)aryl triflates. This methodology is successfully applied to the synthesis of new valuable P-stereogenic phosphonium triflates.

Article titled “Arynes in a Three-Component Coupling Reaction: Straightforward Synthesis of Benzoannulated Iminofurans” by hiroto Yoshida et al. published in Angewandte Chemie International Edition, 2004, 43 (30), pages 3935-3938 reports a variety of benzoannulated iminofurans obtained from an aryne, an isocyanide, and aldehyde in modest to high yields.

Article titled “Multicomponent reactions involving arynes, quinolines, and aldehydes” by A Bhunia et al. published in Org. Lett., 2013, 15 (17), pp 4620-4623 reports the multicomponent reaction involving arynes, quinolines, and aldehydes leading to the diastereoselective synthesis of benzoxazino quinoline compounds in good yields proceeding via 1,4-zwitterionic intermediates. In addition, the synthetic potential of various carbonyl compounds in this reaction as well as the utility of isoquinoline as the nucleophilic trigger has been examined.
Multicomponent reaction using aryne is known, but utilizing phosphine as the nucleophilic trigger is very rare. Although nucleophilic phosphine-catalysis is a powerful tool for the construction of various carbocycles and heterocycles, the reactions where phosphines are incorporated in the final product are rare, and the reports on phosphine addition to highly electrophilic arynes are scarce. Interestingly, however, the utility of the phosphine as a substrate, which is incorporated in the final product thus constituting multicomponent reactions (MCRs) are not well-explored compared to nucleophilic phosphine catalysis
The inventors developed the phosphine triggered multicomponent reaction of arynes and aldehydes, which takes place via the formal [3+2] cycloaddition of initially generated 1,3-phosphonium zwitterion from phosphine and aryne with aldehydes, wherein the process is transition-metal free and the said multicomponent reaction afford high yield and selectivity of stable pentacovalent phosphoranes based on the benzooxaphosphole system.